Apparatus for vaporizing liquefied gas



Sept. 12, 1950 E. w. EVANS 2,522,026

APPARATUS FOR VAPORIZING LIQUEFIED GAS Filed Dec. 26, 1945 LPG VAPOR O00 n 9006 L\\\\\\\\\\\\\\\\\\\ INVENTOR. E. W. E VA N 5 "www ATTORNEYSPatented Sept." 12, 1950 APPARATUS FOR VIRIZING LIQUEFIED Edmond W.Evans, Bartlesville, Okla., assigner to Phillips Petroleum Company, acorporation of Delaware Application December 26, 1945, Serial No.637,279

8 Claims. 1

This invention relates to evaporators. In one of its more specificaspects it relates to evaporators for use in the evaporation ofliquefied normally gaseous materials. My evaporator has special utilityin the liquefied petroleum gas field and in many installationsrelatively large quantities of such material need to be transformed fromthe liquid state to the gaseous state. Such hydrocarbons as propane orbutane are compressed and liquefied and transported and stored in theliquefied condition. Then prior to use of the hydrocarbon as fuel, itmust be vaporized. It is in this vaporization step that my particularevaporator finds special utility.

Further, such hydrocarbon gases are usually processed and handled in adry condition, that is, substantially free from moisture. Publicutilities distributing propane, either in the diluted or undiluted form,complain that because propane as conventionally vaporized is extremelydry, and because their metering and rate schedules are based on a watersaturated gas, there is a loss of about 3% in volume. To state theproblem conversely, the consumer receives a dry gas whereas the B. t. u.requirements are based upon a water saturated gas. r

Such public utilities frequently have occasion to vaporize theseliquefied hydrocarbons at rather rapid rates and under such conditionsheat exchange problems may be acute. Vaporization of liquids is, ofcourse, endothermic. For a conventional evaporator or heat exchangerthere is a definite limitation on the rate of heat transfer throughmetal tubes. A further limitation exists on the rate of heattransferthrough metal tubes due to the formation of an insulating iilm of vaporadjacent exchanger tube surfaces when certain temperature diierentialsare exceeded.

An object of my invention is to provide an evaporator which overcomesthe above mentioned difficulties.

Another object of my invention is to provide a liquefied gas evaporatorwhich is capable of evaporating such liquid at high rates.

Still another object of my invention is to provide a liquefied petroleumgas evaporator which is adapted to the evaporation of such liquids athigh rates and at the same time is adapted to moistening the gases formetering purposes.

Still other objects and advantages will be apparent to those skilled inthe art from a careful study of the following disclosure and theattached drawing which respectively describes and illustrates apreferred embodiment of my invention.

The drawing illustrates in sectional elevation a preferred form of myapparatus.

Referring now to the figure of the drawing, a liquefied gas from asource, not shown, and dowing through a line I and a pressure reducingvalve 2, enters my evaporator by way of an inlet line 3. The evaporatorbody is merely a cylindrical tank 4, vertically disposed and about halffilled with water 6. The liquefied gas inlet tube 3 extends into thelower portion of the tank some llttle distance so that liquid enteringthe tank may be discharged well into the body of the water.

`Steam from a source, not shown, and flowing through a line 6 passes ailow control valvel and enters the tan through an inlet line l. Thesteam, also, is p eferably discharged well into the body of the waterand at a point more or less near the inlet point of and substantiallycountercurrent to the iiow of liquid from conduit 3. To preventoverheating or underheating of the water, a temperature responsivedevice t is inserted into the body of water as shown. A connection fromthis temperature responsive device connects with the motor valve 'l forcontrolling the now of steam. This device is so operated that as thewater in the vessel becomes cooled to below a certain predeterminedtemperature more steam is admitted through valve 1. In case the waterbecomes too warm or is heated to a temperature higher than apredetermined value. the temperature responsive device operates tothrottle or to close oif the flow of steam. Such a condition as thelatter might exist at times when the ow of liquefied gas to beevaporated stops for one reason or another.

An outlet pipe Il is provided for removing excess water from the vesselat times when condensation of steam to water is more rapid than theevaporation of the water into the vaporized gas. A liquid levelcontroller Il is responsive to the level of the water within the vesseland functions to open or to close a motor valve I2 in the water line Il.This assembly is so acliusted that when the water level reaches acertain maximum height the oat controller I I operates to open the motorvalve I2 and permit water to flow in the direction indicated by thearrow since the pressure within the vessel is at all times greater thanatmospheric. In like manner when the waterslevel reaches a certainminimum stage the float II operates to close valve I2. As a secondminimum level is reached controller II operates to open valve Il toadmit additional water into the system through line Il, pump Il and lineIl. As the desired water level withinV the tank is reached controller II once more actuates valve I1 to close it.

At least several bailles Il are provided in the upper gas containingportion of the vessel to assist in preventing or at least minimizingentrainment oi' liquid in the vapors or gas passing out from the top ofthe vessel. A gas outlet line Il leads from the vaporizer tank above thebellies to a gas main, service lines. or other disposal or use, notshown.

In the operation of my apparatus and system as herein described, liquidpropane, or other liqueiied petroleum gas, enters my evaporator by wayof line I. pressure reducer 2 and inlet line I from such a source as astorage tank or transportation tank car, not shown. Liquid propane-has avapor pressure of about 180 to 190 pounds per square inch at about 100F., and in the summer season storage pressure may frequently approachthis value or even exceed it depending upon the location of storagetanks. The liqueed gas at storage pressure then passes through thepressure reducer 2 in which pressure may be reduced to that necessary toforce the gas through a gas main or even a network of gas mains, as inthe case of a municipal distribution system. Such gas main pressures arecomparatively low, as for example from a few pounds pressure up to ashigh as 10 to 20 or even 25 pounds per square inch. The exact value of agiven gas main pressure for pressure reduction purposes through reduceris immaterial since the pressure reduction may be to any desired value.

Any pressure reduction in valve 2 will cause considerable cooling, andunder some conditions it might be advisable to supply heat to the valve.

The liquefied gas then at a reduced pressure enters my evaporatorthrough line 3 and the liquefied gas comes directly in contact with thewarm water 5. By maintaining the temperature of the water at any desiredvalue by the addition of steam from the steam inlet line 8, heatexchange directly from the warmed water to the evaporating liquefiedpetroleum gas is rapid and efcient. In order to maintain the watertemperature at any optimum value, I use a temperature responsive device9 which functions to open the steam valve 1 when the temperature of thewater decreases below a predetermined value or to close the valve whenthe water temperature exceeds this value. Such a temperature controllermay be set to control the temperature at any desired value. 'I'his typeof equipment is standard and commercially available and its use isunderstood by those skilled in the art.

The desired operating temperature of the water is a result of severalconsiderations. It is obvious that the higher the water temperature themore rapid will be the evaporation of the liquefied gas. A secondconsideration is the amount or relative proportion of water vapordesired to be added to the gas for metering purposes. The amount ofwater vapor carried by the evaporating gas is a direct function oftemperature, the higher the temperature the faster is the rate of waterevaporation. The specific temperature carried will probably bedetermined largely from the water vapor pressure consideration and theamount of water vapor desired to be added to the gas. The exact amountof water vapor to be added to a gas forms in reality no part of myinvention since the water vapor will be added in each installationaccording to local conditions, and these may vary from place to placeand even in one location from time to time. One important function of myapparatus is that I can add water vapors to the gas in substantially anydesired amount by merely controlling the heat exchanger watertemperature.

In my evaporator I accomplish a direct heat exchange between the waterand the evaporating liquefied gas which type of exchange operation isvery eillcient. Indirect heat exchange through metal is at bestconsiderably slower than the direct exchanging as herein described.Other disadvantages of indirect exchanging have been hereinbeforementioned. Under certain conditions, as for example, at summertimetempera-- tures, steam condensation may not provide suiiicient water tomaintain a desired liquid level in tank 4, and water may need be addedthrough a water inlet line I6, pump I8, and by the float controllerH-valve I1 assembly.

The particular means as herein described for carrying out the heatexchange-evaporation process of my invention is not critical since varilations and modifications may be made and yet employ direct heattransfer. For example, the water may be withdrawn from the evaporatortank and passed through a heating coil, then back to the tank again. Inthis case no steam condensate will increase the water volume as in mydetailed example, and water will then need be added to maintain aconstant level within the evaporator vessel. A float controller-motorvalvewater pump assembly can be used. When the water level drops asindicated by the float, this latter opens a valve and starts a pump.Then as the water level increases to a predetermined value, the floatoperates to stop the pump and close the valve so the water will not backiiow in any manner.

A safety valve I5 of any desired type and adjustable to flow off at anydesired pressure should be used for obvious reasons.

Still other means of heating the water may be employed, as for example,use of a steam coil in the bottom of the vessel 4, but even in this casethe hot water is the medium for transferring heat to the vaporizing gas.

Apparatus and materials to be used in such an installation is standardand may be purchased on the market. No special equipment is needed.

From the above explanation it will be obvious to those skilled in theart that many variations and modifications of my preferred embodimentmay be made and yet remain within the intended spirit and scope of myinvention.

Having disclosed my invention, I claim:

1. A method for simultaneously vaporizing a liquefied petroleum gas andadding moisture to the extent of a maximum of approximately 3% by volumeof the evaporated gas comprising passing the liquefied petroleum gasinto direct heat exchange relation with steam and water at such atemperature as will evaporate the liquefied gas and will vaporizesufcient water to produce about 3% moisture in the vaporized petroleumgas; and removing the vaporized gas containing moisture as the productof the process.

2. A method for vaporizing and humidifying liquefied petroleum gascomprising passing the liquefied petroleum gas into direct heat exchangewith water at a temperature to provide rapid evaporation of the gas;maintaining the temperature of said water by direct heat exchange withsteam; and removing the evaporated gas.

3. An improved process for vaporizing a liquefied petroleum gas andcontrollably humidifying the resulting vapor in a confined vaporizingzone containing a body of water, which comprises the steps ofcontinuously introducing into said body of water in the lower portion ofsaid vaporizing zone a streamof liquefied petroleum gas; simultaneouslyand continuously introducing into said body of water in said zone a'stream of steam in an amount suilicient 11o-provide latent heat forvaporizing said liqueiied petroleum gas and maintaining the temperatureof said body of water and said vaporized hydrocarbon at such a pointthat eliluent vapors contain about 3% by volume of water vapor;andremoving from said body of water and vaporizing` zonev resultingvaporous troduction will4 be substantially counter-current to the Ilowof said petroleum gas stream',l a stream of steam in an amountsuilicient to provide latent heat for vaporizing said liqueiiedpetroleum gas and maintaining the temperature of said body of water andsaid vaporized hydrocarbon at such a point that eilluent vapors containabout 3% by volume of water vapor; and removing from said body of waterand vaporizing zone resulting humidied vapor.

5. An improved process for vaporizing liquid propane and controllablyhumidifying the re' sultin'g vaporous propane in a confined vapor--izing zone containing a body of water, which comprises the steps ofcontinuously introducing into said body of Water in the lower portion ofsaid vaporizing zone -a stream of liquid propane; simultaneously andcontinuously introducing into said body of water in said zone, at apoint substantially opposite the propane introduction point and in closeenough proximity that the introduction will be substantiallycounter-current to said liquid propane streama stream of steam in anamount sufficient to provide latent heat for.r

Avaporizing said liquid propane and maintaining of water in saidchamber; `a liqueed gas conduit protruding into said body of water insaid chamber on substantially lthe same level as said steam conduit andto a point so that the outlet for said gas conduit is in relativelyclose proximity to the outlet of said steam conduit, whereby liqueiledgas and steam are emitted from their respective conduits into said bodyor water to rorm amix- 1 ture oi' gas and steam; control meansresponsive to temperature within said chamber; Ya valve in in said drainmeans operatively connected to said liquid levelI responsive controlmeans;

means for introducing water into said chamber; a valve in said waterintroducing means operatively connected to said liquid level responsivecontrol means; a gas outlet from the upper portion of said chamber; andmeans for reducing entrainment of liquid in the gas passing out of saidchamber.

7. A liquefied gas vaporizer device comprising in combination a coniinedchamber; a body of waterV in a substantial portion of said chamber; asteam conduit protruding substantially into said body of water in saidchamber; a liqueed gas conduit also protruding into said body of waterin said chamber; control means responsive to temperature within saidchamber; a valve in said steam conduit regulating steam ow therethroughand operatively'connected to said temperature responsive control means;a pressure reducing valve in --said liquefied gas conduit; control meanscommunicating with said chamber and responsive =to the liquid leveltherein; means for draining water fromsaid chamber; a valve in saiddrain means .for reducing entrainment of liquid in the gas passing outof said chamber.

8. A liqueed gas vaporizer device comprising in combination aconnedchamber; a steam conduit protruding substantially -into the lowerportion of` said chamber; a liquefied gas conduit protruding into saidchamber from a direction other than that in which said steam conduit ismaintained and on substantially the same level as said steam conduit,the outlets of said conduits being in relatively close proximity to one.another; control meansY responsive to temperature within said chamber; avalve in said steam conduit for regulating steam flow therethrough andoperatively connected to said temperature responsive control means; apressure reducing valve in said liqueiied gas'conduit; control meanscommunicating with said chamber and responsive to liquid level with-V insaid chamber; drain means in the lower p0rtion of said chamber; a valvein said drain means operatively connected to said liquid levelresponsive control means; liquid inlet means communicating with thelower portion 'of said chamber; a valve insaid liquid inlet meansoperatively connected t'o said liquid level responsive control means; agaseoutlet in the upper portion of said chamber and baille members inthe upper portion of said chamber and below said gas outlet therein.

EDMOND W.V EVANS.

REFERENCES CITED The following references are of record in the ille o1this patent:

said steam conduit regulating steamiow therethrough and operativelyconnected to said temperature responsive control means; a pressurereducing valve in said liqueiied gas conduit; control meanscommunicatingwith said chamber and responsive to the liquid leveltherein; means for draining water from said chamber; a valve Hoagland...-----.-..Mar. 1l, `194:1

8. A LIQUEFIED GAS VAPORIZER DEVICE COMPRISING IN COMBINATION A CONFINEDCHAMBER; A STEAM CONDUIT PROTRUDING SUBSTANTIALLY INTO THE LOWER PORTIONOF SAID CHAMBER; A LIQUEFIED GAS CONDUIT PROTRUDING INTO SAID CHAMBERFROM A DIRECTION OTHER THAN THAT IN WHICH SAID STEAM CONDUIT ISMAINTAINED AND ON SUBSTANTIALLY THE SAME LEVEL AS SAID STEAM CONDUIT,THE OUTLETS OF SAID CONDUITS BEING IN RELATIVELY CLOSE PROXIMITY TO ONEANOTHER; CONTROL MEANS RESPONSIVE TO TEMPERATURE WITHIN SAID CHAMBER; AVALVE IN SAID STEAM CONDUIT FOR REGULATING STEAM FLOW THERETHROUGH ANDOPERATIVELY CONNECTED TO SAID TEMPERATURE RESPONSIVE CONTROL MEANS; APRESSURE REDUCING VALVE IN SAID LIQUEFIED GAS CONDUIT; CONTROL MEANSCOMMUNICATING WITH SAID CHAMBER AND RESPONSIVE TO LIQUID LEVEL WITHINSAID CHAMBER; DRAIN MEANS IN THE LOWER PORTION OF SAID CHAMBER; A VALVEIN SAID DRAIN MEANS OPERATIVELY CONNECTED TO SAID LIQUID LEVELRESPONSIVE CONTROL MEANS; LIQUID INLET MEANS COMMUNICATING WITH THELOWER PORTION OF SAID CHAMBER; A VALVE IN SAID LIQUID INLET MEANSOPERATIVELY CONNECTED TO SAID LIQUID LEVEL RESPONSIVE CONTROL MEANS; AGAS OUTLET IN THE UPPER PORTION OF SAID CHAMBER AND BAFFLE MEMBERS INTHE UPPER PORTION OF SAID CHAMBER AND BELOW SAID GAS OUTLET THEREIN.